All lanes : Anti-ERp72 antibody (ab109869) at 1/1000 dilution

Lane 1 : Rat liver microsome extracts
Lane 2 : Mouse liver microsome extracts
Lane 3 : Human liver microsome extracts

Predicted band size: 73 kDa
Observed band size: 72 kDa why is the actual band size different from the predicted?

ab109869 at 10 µg/ml staining ERp72 in formalin-fixed, paraffin-embedded Human cerebellum tissue after heat induced antigen retrieval in pH 6.0 citrate buffer.
After incubation with the primary antibody, slides were incubated with a biotinylated secondary antibody, followed by alkaline phosphatase-streptavidin and chromogen.

ab109869 at 10 µg/ml staining Erp72 in formalin-fixed, paraffin-embedded Human placenta tissue after heat induced antigen retrieval in pH 6.0 citrate buffer.
After incubation with the primary antibody, slides were incubated with a biotinylated secondary antibody, followed by alkaline phosphatase-streptavidin and chromogen.

ab109869 at 10 µg/ml staining Erp72 in formalin-fixed, paraffin-embedded human prostate tissue after heat induced antigen retrieval in pH 6.0 citrate buffer.
After incubation with the primary antibody, slides were incubated with a biotinylated secondary antibody, followed by alkaline phosphatase-streptavidin and chromogen.

ab109869 at 10 µg/ml staining Erp72 in formalin-fixed, paraffin-embedded Human testis tissue after heat induced antigen retrieval in pH 6.0 citrate buffer.
After incubation with the primary antibody, slides were incubated with a biotinylated secondary antibody, followed by alkaline phosphatase-streptavidin and chromogen.